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Abstract
A study of the ultrastructure of the round window membrane revealed several interesting characteristics of functional significance. The membrane consists of three layers: (1) An external layer faces the tympanic cavity and varies from one to two cells in thickness. It is composed of four types of cells: osrniophilic, osmiophobic, dark granulated and goblet cells. The free surface has niicrovilli and is coated with an amorphous substance. (2) An internal layer, facing the scala tympani, is one cell thick and lacks rnicrovilli, but an occasional kinocilia was observed. The cells have very long thin cytoplasmic processes and extensive endoplasmic reticulum. Secretory granules are present, and it appears that these cells synthesize a substance, possibly glycogen. Blood vessels were observed resting on the free surface. (3) A middle layer of connective tissue contains all the normal components and is interspersed with blood vessels and unmyelinated nerve fibers. Both collagen and elastic fibers were found to be quite evenly distributed in a radial arrangement throughout this layer.